Generally, semiconductor devices are electrical devices that utilize a semiconductor as a material component. Semiconductor devices are used in a variety of electronic applications, such as computers, cellular phones, personal computing devices, and many other applications. Home, industrial, and automotive devices that in the past comprised only mechanical components now have electronic parts that require semiconductor devices, for example.
Semiconductor devices are manufactured by depositing many different types of material layers over a semiconductor workpiece or wafer, and patterning the various material layers using lithography. The material layers typically comprise thin films of conductive, semiconductive, and insulating materials that are patterned and etched to form integrated circuits (IC's). There may be a plurality of transistors, memory devices, switches, conductive lines, diodes, capacitors, logic circuits, and other electronic components formed on a single die or chip.
One type of transistor device is a complimentary metal oxide semiconductor (CMOS) device, in which a p-channel metal oxide semiconductor (PMOS) transistor and an n-channel metal oxide semiconductor (NMOS) transistor are used in complimentary configurations.
In semiconductor devices, electron mobility changes when silicon crystals are strained. As CMOS devices are scaled down in size, stress engineering is becoming more important, in particular due to the fact that electron and hole mobility change when silicon crystals are strained. In transistor designs, the effects of stress are actively used, such as the effects of tensile and compressive stress, to raise mobility and increase speed of transistors.
Stress is introduced by applying tensile liners and by forming germanium-containing materials in the source, drain, and channel regions, for example. However, PMOS transistors respond differently to stress than NMOS transistors, and thus, it can be challenging to manufacture CMOS devices with optimized stress.
Thus, what are needed in the art are improved methods of creating and utilizing stress to optimize the performance of semiconductor devices.